Radiotelegraphy



are. MARX AND L. F. FULLER.

RADIOTELEGRAPHY.

APPLICATION HLEp AUG-I3. 1917.

Patented June 22, 1920.

INVENTORS R. s. MARX- F. FULLER UNITED STATES,

PATENT OFFICE.

ROLAND G. MARX, OF PALO ALTO, AND LEONARD F..FULLER OF SAN FRANCISCO,CALIFORNIA, ASSIGNORS TO FEDERAL TELEGRAPH COMPANY, OF SAN FRAN- CISCO,CALIFORNIA, A CORPORATION OF CALIFORNIA.

RADIOTELEGRAPHY.

. specification of Letters Patent. Patented June 22, 1920.

Application filed August 13, 1917. Serial No. 185,907.

' To all whom it may concern:

Be it known that We, ROLAND G. MARX and LEONARD F. FULLER, citizens ofthe United States, and residents, respectively, of

lalo Alto, Santa Clara county, and the city and county of San Francisco,both in the State of California, have invented certain new and usefulImprovements in Radio-' telegraphy, of specification.

The invention relates to means of signaling and particularly to meansfor signaling with are radio transmitters.

which the following is a An object of the invention is to provide meansfor signaling by varying the antenna current.

Another object of the invention is to provide means for signaling whichrequires the handling of only relatively small. currents.

A further object of the invention is to provide means for successivelyestablishing and interrupting the arc.

The invention possesses other advantageous features, some of which, withthe foregoing, will be SQtfOIllll at length in the followingdescription, where we shall outline in full,

that form of the invention which we have selected for illustration inthe drawings accompanying and forming part of the present specification.It is to be understood,

however, that the invention as expressed inthe'claims is not limited tothe specific embodiment shown in the drawings.

Referring to said drawings: Figure 1 is a diagrammatic representation ofone form of the system which is particularly applicable to high-poweredstations.

Fig. 2 is a diagrammatic representation of a form of the system which isparticularly applicable to low-powered stations.

The present system providesa means of signaling which contemplates avariation of the antenna current by varying the resistance of theantenna circuit and the resistance is inserted without opening orclosing the antenna circuit. \Vhen the resistance of the antenna circuitis increased, the antenna current and the current across the arc is de-'creased, the amount of decrease depending upon the resistance added. Inpractice we prefer to reduce the radiation, that is antenna current, tonearly zero. NVith large arcs, that is, high-powered arcs, the arc doesnot go out when the arc current is reduced,

but; small arcs are more unstable and are liable to. go out and in orderto insure reliability ofoperation, we prefer to employ means forreigniting the arc, should it become extinguished.

It is practically impossible to insert into and remove from the antennacircuit at telegraphic speed, a sufficient resistance to vary theradiation to nearly zero, or to reduce it any considerable amountwithout severe sparking. In accordance with our inven tion we introduceinto the system, a resistance which has the equivalent effect ofintroducing the resistance. directly into the antenna circuit and thisis so introduced that the handling of large currents and sparking orarcing at the contacts is'practically avoided.

The transmission system comprises an arc oscillation generator 2 whichis grounded on one side, preferably the negative, and

connected on the other side to the antenna 3 through the variableinductance 4. Direct current'is supplied to the arc generator by thegenerator 5', and a choke coil 6 is arranged in the lead '7 connected tothe an- The are is subjected tenna side of the arc. to a strongtransverse magnetlc field produced by the magnet coils 8 which may beloading inductance 4 which becomes in effect an auto-transformer. Weprefer to make the value of the resistance in ohms substantially equalto the reactance in ohms at radio frequency of the turns of theinductance which are shunted by the resistance circuit in order to causea maximum energy loss in the resistance.

.When the key 13 is open no current is flowing in the resistancecircuit, so that the key may be closed without producing appreciablearcing. As soon as: the key is closed, the arc current is reduced-tonearly zero, so that when the key is opened, no appreciable arcing willoccur. \Vhen the key is pressed to open the resistance circuit the fullcurrent is delivered-to the antenna. In small stations the are is oftennot sufficiently stable to permit of this action, but goes out when theresistance losses occur in the antenna circuit, hence means are providedfor reigniting it.

In Fig. 2 we have shown one means which may be employed in reignitingthe are, this means being so arranged thatthe arc is ignited as theresistance circuit opened. Connected across the arc is a spark circuitcontaining the spark gap 14,.the secondary of the transformer 15 and thecapacity 16, shunting the secondary. A stopping resistance 17 isarranged between the spark gap and the antenna side of the are toprevent direct current sutlicient to maintairtan are across the sparkgap from following the radio frequency current across the spark gap andpassing through the secondary. The primary of the transformer is inseries with an alternating current generator 18 and a switch 19 isattached to the key 13 by an insulating rod 21. \Vhen the resistancecircuit is opened, the circuit through the primary of the transformer isclosed, producing a high potential in the spark circuit and producing aspark across the spark gap which sets up radio frequency surges whichignite the arc.

\Ve claim:

1. An are system for radio signaling, comprising a current supply andantenna circuit connected to an arc and means for ap preciablyincreasing the resistance of the an tenna circuit whereby the-current inthe antenna is reduced below signaling value.

2. An arc system for radio signaling, com prising a current supply andantenna circuit connected to an arc, an inductance in the antennacircuit and a circuit containing an appreciaba resistance arranged inshunt around said imluctancc. the closing of the resistance circuitserving to reduce the arc current below signaling value.

3. .\n arc system for radio signaling, comprising a current supply andantenna circuit connected to an arc, an inductance in theantennacircuit, a circuit containing an ape preciable resistance in shuntaround said in ductance and means for opening and closing the resistancecircuit. the closing of the resistance circuit serving to reduce the arccurrent below signaling value.

4. An are system for radio signaling, com- )risin it current SLl))l andantenna (11'- cuit connected to an are, an inductance in the antennacircuit, and a circuit containing resistance arranged to shunt saidinductance, the value of the resistance in ohms approximating thereactance at radio frequency in ohms of the shunted inductance.

5. An arc system for radio signaling, comprising a current supply andantenna circuit connected to an are, an inductance in the antennacircuit, a circuit containing an appreciable resistance arranged inshunt around the inductance, the value of the resistance in ohmsapproximating the reactance at radio frequency in ohms of the shuntedinductance, and a signaling key in said shunt circuit.

6. An are system for radio signaling, comprising a current supply andantenna cir-- cuit connected to an are, an inductance in the antennacircuit, an appreciable resistance connected across a portion of theinductance and a signaling key in the resistance circuit, closing of thekey serving to reduce the arc current below signaling value.

7. An are system for radio signaling, comprising an are subjected to astrong transverse magnetic field, a current supply and antenna circuitconnected to the are, means for decreasing the antenna current wherebythe arc is extinguished and means for reigniting the arc.

8 An are system for radio signaling, cornprising an are subjected to astrong transverse magntic field, a current supply and antenna circuitconnected to the are, an inductance in the antenna circuit, a circuitcontaining resistance shunting a portion of said inductance, a signalingkey in said re sistance circuit, and means operative in time with theopening of said key for producing a spark across the are.

9. An are system for radio signaling, comprising a current supply andantenna circuit connected to an are, an inductance in the antennacircuit, a circuit containing resistance shunting a portion of saidinductance, a signaling key in said resistance circuit, the closing ofsaid key serving to extinguish the arc and means for reigniting the are.

In testimony whereof I have hereunto set my hand at Honolulu, H., this19th day of July, 1917.

ROLAND G. MARX. In testimony whereof I have hereunto set my hand at SanFrancisco, Calif, this 31st day of July, 1917.

LEONARD F. FULLER.

